Midpoint potential of signal II (slow) in Tris-washed photosystem-II particles |
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Authors: | Alain Boussac Anne Lise Etienne |
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Institution: | Centre National de la Recherche Scientifique, Laboratoire de Photosynthèse, BP, No. 1, 91190 Gif-sur-Yvette France |
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Abstract: | In Tris-washed Photosystem-II particles we are able to induce an EPR signal in the dark by addition of an iridium salt (K2IrCl6). This signal is attributed to signal IIs (slow) (D+) and the redox titration gives an Em value of 760 mV for the couple . On the basis of our previous studies on the equilibrium between D+Z and DZ+ (K = 104) (Boussac, A. and Etienne, A.L. (1982) Biochem. Biophys. Res. Commun. 109, 1200–1205), we therefore attribute a value of 1 V for the Em of the couple. A second effect of K2IrCl6 is to modify the spectral characteristics of signal II. We conclude that K2IrCl6 is able to change the environment of the species from which signal IIs and signal IIf originate. |
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Keywords: | Photosystem II Redox potential EPR Signal II (Pea chloroplast) Z D PS I Photosystem I PS II Photosystem II magnetic field DPPH 1 1-diphenyl-2-picrylhydrazyl |
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